RU2665439C1 - Hybrid sorbent - Google Patents

Abstract

FIELD: technological processes; chemistry.SUBSTANCE: invention relates to the sorbents for the selective sorption of arsenic from water. Hybrid sorbent based on an anion-exchange polymer matrix with hydrated iron oxides is proposed. Hydrated iron oxides are present in the matrix in the form of particles, that are for the most part amorphous ferrihydrite, its proportion is not less than 80 % of the total mass of hydrated iron oxides and having a microporous structure. Polymer matrix is a macroporous fibrous and/or granular material, the content of anion-exchange groups in the polymer matrix is at least 6.0 mmol/g.EFFECT: technical result is the development of a new hybrid sorbent with increased sorption kinetics simultaneously of both As (III) and As (V) arsenic forms.1 cl, 5 dwg, 1 tbl

Description

The invention relates to hybrid sorbents for removing arsenic compounds from water and is intended for use in water purification devices.

In many countries, due to the lack of surface water, groundwater is used as a source of fresh water.

An important problem when using groundwater is the problem of arsenic pollution, which is typical for about 20 countries, for example, the USA and Chile. On the territory of Russia, the regions containing arsenic in groundwater include the territories of the Transbaikal, Perm, Stavropol, Khabarovsk Territories, the Republic of Tuva, the Magadan and Penza Regions, as well as the Republic of Dagestan. Arsenic in water leads to cancer and skin lesions. In water, arsenic is contained in the form of compounds of trivalent arsenic (hereinafter - As (III)), for example, arsenites or arsenous acid and compounds of pentavalent arsenic (hereinafter - As (V)), for example, arsenates. Sorbents for removing arsenic are known in the art. The most commonly used material is a mixture of iron oxides, iron hydroxides and iron oxyhydroxides in various proportions (hereinafter referred to as hydrated iron oxides). Depending on the ratio of the components, different versions of hydrated iron oxides are known that differ in their properties.

Sorbents known in the art are obtained by distributing particles of hydrated iron oxides in an inert polymer material or containing ion-exchange groups for fixing iron ions. The introduction of hydrated iron oxides into the polymer material is carried out, for example, by mechanically dispersing particles of hydrated iron oxides in the polymer material or by forming particles of hydrated iron oxides directly in the polymer material through the formation of an intermediate structure in the material, followed by precipitation of particles of hydrated iron oxides. Such sorbents are called hybrid.

BACKGROUND

A hybrid sorbent for removing arsenic compounds according to US Pat. No. 4,576,969 is known in the art (publ. March 18, 1986, prior. October 13, 1983, IPC C08D 5/20, C08F 8/10, applicant Unitika Ltd (Japan)). A hybrid sorbent is an ion-exchange phenolic resin with a metal oxide fixed in its structure. Hybrid sorbent is prepared as follows. In the first stage, the phenol resin is precondensed, to which, while it is still in a fluid state, a salt or metal oxide, for example, sulfate, hypochlorite, nitrate, acetate, iron, silver, aluminum, zinc, etc., is added. Then, the condensation reaction of the resulting mixture is carried out, thereby fixing the metal oxide or salt in the resin structure. As the reaction medium, for example, carbon tetrachloride, chloroform, dichloromethane are used. After the condensation reaction, the resulting material is separated from the reaction medium and an alkylating agent, for example, alkali metal hydroxide or sodium carbonate, is added. The structure of the obtained hybrid sorbent is a cross-linked phenolic resin, inside which a multivalent metal hydroxide is fixed. The sorbent has a low degree of swelling, high wear resistance, the sorbent granules have almost no cracks and are almost not deformed.

The sorption capacity of the arsenic hybrid sorbent obtained in US 4,576,969 is 33 mg / g at a very low rate of water flow through the material (250 ml / h), which is extremely inefficient. This value of speed can be explained by the fact that the superdense crosslinked structure of the hybrid sorbent impedes the flow of water. The low rate of water flow through the sorbent significantly narrows the scope of its application until only laboratory tests are carried out, since on an industrial scale such a speed value is unacceptable. This sorbent cannot be used to obtain drinking water either, since phenol and formaldehyde are used in its preparation. Even the residual content of these substances in the obtained resin leads to their washing off into the purified water during the passage of water through the material, which is unacceptable for drinking water.

A hybrid sorbent is known from the prior art according to patent application US 2011/0056887 (publ. 03/10/2011, prior 08.09.2009, IPC C02F 1/42, C02F 103/06, C02F 103/02, C02F 103/10, C02F 101 / 10, Applicant LANXESS DEUTSCHLAND GMBH (DE); LANXESS CORPORATION (US)). A hybrid sorbent is a macroporous monodisperse anion-exchange material with hydrated iron oxides deposited on it. It is intended mainly for the removal of arsenic ions from water and aqueous solutions, in particular, H ₂ AsO ₄ ^- , H ₂ AsO ₄ ^- , HAsO ₃ ^2- , AsO ₄ ^3- , H ₃ AsO ₃ , H ₂ AsO ₃ ^- , HAsO ₄ ^2- , HAsO ₄ ^2- . The content of iron (III) in the hybrid sorbent is 16% by weight.

The application of hydrated iron oxides on the anion-exchange material is carried out in the following way. Denounced water is added to the anion exchange material with continuous stirring at room temperature. Then, iron (III) sulfate is added to the resulting suspension and stirring is continued for 90 minutes. After that, an aqueous solution of sodium hydroxide NaOH is added until a pH7 solution is reached. Next, an aqueous solution of sodium chloride NaCl is gradually added to the solution, and stirring is continued for 30 minutes. The solid phase is separated from the resulting suspension, which is the final product.

The disadvantages of the hybrid sorbent according to patent application US 2011/0056887 is the low sorption ability of arsenic ions As (III) and As (V), therefore, the hybrid sorbent can be used for water or an aqueous solution in which the concentration of arsenic is not more than 10 Mr ( As) / l.

The sorbent according to the patent US 7,811,360 (publ. 12.10.2010, prior. September 25, 2001, IPC B01D 53/04, applicant LANXESS Deutschland GmbH (DE)), consisting of hydrated iron oxides, namely goethite oxyhydroxide α-, is known from the prior art. FeO (OH), presented in the form of elongated granules or short fibers.

The patent presents three options for the sorbent: sorbent 1, sorbent 2 and sorbent 3rd three methods for its preparation, respectively.

Sorbent 1 consists of 100% goethite α-FeO (OH) and represents agglomerates of short elastic fibers with a diameter of 30-50 nm and a length of 0.2 to 2 mm with high mechanical characteristics, resistant to compression, hydraulic stress and abrasion .

Sorbent 1 is prepared as follows. Iron (II) sulfate FeSO _{4 is} dissolved in water and the resulting solution is cooled to a temperature of 14 ° C. Magnesium sulfate MgSO ₄ ⋅ 7H ₂ O is added to the solution. The solution is homogenized at a solution temperature of 14 ° C. Then sodium hydroxide NaOH is added to the solution and oxidized by sparging of atmospheric oxygen until a precipitate containing about 99.5% goethite precipitates. The precipitate is separated by decantation and squeezed. A mass of sediment is passed through metal presses with openings of 7 mm to form elongated granules or short fibers of the final sorbent. The sorbent fibers are dried on a belt dryer to a residual moisture content of 3%.

Sorbent 2 consists of goethite α-FeO (OH) and magnesium hydroxide Mg (OH) ₂ . The sorbent consists of short fibers collected in agglomerates, while the fibers are bonded to each other with amorphous layers.

Sorbent 2 is prepared as follows. A suspension containing oxyhydroxide - goethite α-FeO (OH) in an amount of 50 g / l is added to an aqueous solution of MgSO ₄ . After that, sodium hydroxide NaOH was added to the solution with continuous stirring for 15 minutes. The suspension is washed on a suction filter to obtain a solution with a specific conductivity of 1 mS / cm, the filter cake is dried to a residual moisture content of not more than 2% in a drying oven at 75 ° C.

Sorbent 3 is a 100% goethite α-FeO (OH) in the form of very short needle crystals, collected in dense agglomerates. The specific surface of the sorbent is 102 m ² / g.

Sorbent 3 is obtained by mixing a solution of aluminum sulfate Al ₂ (SO ₄ ) ₃ with goethite particles α-FeO (OH) in an alkaline NaOH solution, followed by separation of the suspension solid phase, washing and drying the resulting sorbent to a residual moisture content of not more than 2%. The size of the needle crystals is from 0.5 to 2 mm.

The main disadvantage of the sorbent according to US patent 7,811,360 is the low degree of removal of arsenic As (III) and As (V) - not more than 50% for each type of arsenic, as well as the low kinetics of sorption of arsenic As (III) and As (V).

Sorption kinetics of sorbent 1:

As (III) on the example of NaAsO ₂ with a concentration of 2.5 mg / l is 1.8 mg (As ³⁺ ) / g (FeO (OH)) ⋅h;

As (V) for the example of Na ₂ HAsO ₄ with a concentration of 2.9 mg / L is 1.5 mg (As ⁵⁺ ) / g (FeO (OH) ⋅h.

Sorption kinetics of sorbent 2:

As (III) for NaAsO ₂ with a concentration of 2.6 mg / L is 1.2 mg (As ³⁺ ) / g (FeO (OH)) ⋅h;

As (V) for Na ₂ HAsO ₄ with a concentration of 2.7 mg / L is 1.5 mg (As ⁵⁺ ) / g (FeO (OH)) ⋅h.

Sorption kinetics of sorbent 3:

As (III) for NaAsO ₂ with a concentration of 2.6 mg / L is 2.0 mg (As ³⁺ ) / g (FeO (OH)) ⋅h;

As (V) for Na ₂ HAsO ₄ with a concentration of 2.1 mg / L is 1.5 mg (As ⁵⁺ ) / g (FeO (OH)) ⋅h.

From this it follows that the sorbent is not effective enough to remove arsenic ions As (III) and As (V).

The hybrid sorbent according to the patent US 7,807,606 is known from the prior art (publ. 05.10.2010, prior 04.09.2003, IPC B01J 21/04, applicant Battelle Energy Alliance, LLC (US)). A hybrid sorbent is a polymer matrix with hydrated iron oxide deposited on it. As the polymer matrix, polyacrylonitrile (hereinafter referred to as PAN) is used — an acrylonitrile homopolymer or a copolymer containing at least about 40% acrylonitrile units. This patent provides a hybrid sorbent and two methods for its preparation.

In the first method for producing a hybrid sorbent, hydrated iron oxides, namely iron oxide, for example, Fe ₃ O ₄ or Fe ₂ O _{3, are} dissolved in concentrated nitric acid. Then PAN is added to the solution to its content in the solution from 3 to 5% and mixed. Next, the resulting solution is sprayed through air nozzles into a NaOH solution. When droplets of the solution enter alkali, they solidify with the formation of solid sorbent granules. The solid granules of the obtained sorbent are removed from the alkaline bath and washed with ethanol, dried at a temperature of about 60 ° C, and then crushed to obtain a homogeneous fraction of the granulated sorbent. The resulting sorbent may contain from 30% to 70% of iron (III).

According to the second production method, hydrated iron oxides are dissolved in dimethyl sulfoxide (hereinafter DMSO), and after the particles of hydrated iron oxides are completely dissolved, PAN is added to the glandular solution. The PAN: hydrated iron oxides ratio is about 1: 5, respectively. Dissolution of PAN is carried out at a temperature of 90 ° C and constant stirring until the fibers of PAN are completely dissolved, after which the temperature is gradually reduced to 40 ° C. The solution is then sprayed through air nozzles into a bath of cold deionized water. When sprayed particles of a solution of PAN with hydrated iron oxides in DMSO get into water, DMSO passes from the solution into deionized water and the formation of solid granules of the hybrid sorbent occurs. After that, the resulting sorbent particles are washed additionally with water with continuous stirring for 30 minutes in order to remove residual DMSO. Next, the obtained granules of the sorbent are dried at a temperature of 40 ° C. The obtained granular hybrid sorbent with hydrated iron oxides contains about 85% hydrated iron oxides and 15% PAN. Sorbent granules have a macroporous structure and good mechanical properties.

Hybrid sorbent for both methods of preparation may contain from 10 to 85% hydrated iron oxides and from 10 to 90% PAN of the total mass of the sorbent. Hydrated iron oxides in a hybrid sorbent are presented in the form of iron (III) in elemental form, iron hydroxide, iron oxyhydroxides and iron oxides. The total iron content in the hybrid sorbent may be from 250 to 700 mg / g.

The sorption capacity of the hybrid sorbent for As (V) is from 7.5 to 10 mg / g.

As a result of the analysis of the patent US 7,807,606 identified the following disadvantages. First of all, this is the low sorption capacity for As (V), as well as the lack of evidence of the claimed sorption ability of As (III) ions. The above compounds of hydrated iron oxides have a crystalline structure and, therefore, are characterized by low sorption ability.

A significant disadvantage of the hybrid sorbent obtained by the method described in the patent is the dissolution of PAN, since when the PAN is dissolved, the fiber loses its ordered structure and properties. In addition, the use of PAN in the form of a fiber with the aim of dissolving it into a liquid form with the subsequent formation of granules from it is impractical.

In addition, to obtain a hybrid sorbent according to the patent US 7,807,606 use PAN that does not have anion exchange properties. From which it follows that the described hybrid sorbent is only a mechanical mixture of PAN and a complex of hydrated iron oxides. The absence of anion-exchange groups in the carrier material (PAN) indicates that iron (III) cations are not able to attach to PAN, and the described hybrid sorbent is a mixture of particles of hydrated iron oxides evenly distributed mechanically between PAN particles, which is also a significant drawback sorbent. Also, in the absence of ion-exchange groups in the sorbent, sorption of heavy metals is impossible.

The prior art hybrid sorbent with hydrated iron oxides obtained by the method described in patent application US 2007/0241057 (publ. 10/18/2007, prior. 04/11/2006, IPC B01J 20/26, applicant Lanxess Corporation (US)) .

To obtain the sorbent, an anion-exchange polymer matrix based on aromatic hydrocarbons, for example, polyvinyl, is used. An aromatic hydrocarbon, an initiator and a pore-forming agent are introduced into the mixture to obtain an anion-exchange polymer matrix to achieve macroporosity of the anion-exchange polymer matrix. After the anion-exchange polymer matrix has been prepared, a solution of an iron (II) salt or an iron (III) salt is incapable of complexing, for example, soluble chlorides, sulfates and nitrates. In the case of using iron (II) salts, they are oxidized to iron (III) salts, for example, atmospheric oxygen. After that, a solution of a substance is added to the suspension, which leads to the formation of hydrated iron oxides, for example, alkali metal hydroxide. The resulting material is laid out on a sieve to remove excess liquid and washed with distilled water.

According to the patent US 7,407,587 (published 05.08.2008, prior. 03.24.2006, IPC C01B 31/08, C02F 1/42, the applicant Layne Christensen Company (US) knows a hybrid sorbent based on an anion exchange resin with hydrated iron oxides and a method for its preparation consisting in treating the anion-exchange resin with an iron (III) salt, followed by treating the resulting material with an alkali solution and final washing of the obtained material with distilled water.The treatment with the iron salt and alkali can be carried out in at least two stages with an interval for washing. anio oobmennoy resin iron brine washing is carried out with sodium chloride enriched with carbon dioxide, after treatment with alkali washing is carried out with distilled water. As salts of iron (III) may be used, e.g., chloride, nitrate, iron acetate (III).

As a result, particles of hydrated iron oxides irreversibly fixed on the surface and in the pores of the anion-exchange resin are formed in the hybrid sorbent prepared by this method.

In US Pat. No. 7,407,587, a hybrid sorbent prepared by the method described above is capable of sorbing anions containing As (V) arsenic from water. With an increase in the amount of iron in the hybrid sorbent, the degree of absorption of As (V) arsenic anions from the solution increases. Moreover, the optimal pH of the solution at which the maximum sorption of arsenic anions As (V) occurs is 6.

The disadvantage of the invention according to the patent US 7,407,587 is the lack of ability of the hybrid sorbent for sorption of arsenic compounds As (III). It should also be noted that the size and porosity of particles of hydrated iron oxides depend on the rate of their formation. With the direct action of alkali metal hydroxide on iron chloride, the exchange reaction occurs almost instantly, which leads to the rapid deposition of iron hydroxide and the formation of large particles with low porosity, which limits the practical use of the sorbent, since the smaller the porosity, the smaller the effective surface area of the sorbent, a larger amount of sorbent must be used to clean a given volume of water, so the water purification device must have a large overall size, which is inconvenient about, for example, for water purification in everyday life.

The prior art hybrid sorbent based on an anion-exchange polymer matrix with hydrated iron oxides for selective removal of contaminants from liquids and the method of its preparation according to patent US 7,291,578 (publ. 06.11.2007, prior. 21.01.2004, IPC B01J 20/26, applicant Arup SenGupta (US)) selected by the applicant as the closest equivalent. A method of obtaining an anion-exchange polymer matrix is as follows. The anion-exchange polymer matrix is enriched with an anionic oxidizing agent, for example, potassium permanganate or sodium hypochlorite and washed. Then the resulting material is treated with a salt of iron (II). In this case, the reaction of oxidation of iron (II) to iron (III) takes place with the transition to the form of hydrated iron oxides and the reduction of the anion oxidizer. Thus, particles of amorphous hydrated iron oxides are formed and fixed in the structure of the anion-exchange polymer matrix. Next, the anion-exchange polymer matrix with hydrated iron oxides is washed with acetone and dried.

The applicant conducted studies of the sorbent, as claimed in patent US 7,291,578. The disadvantages of the sorbent according to the patent US 7,291,578, as well as a comparative analysis of the sorbent of the closest analogue with the claimed hybrid sorbent according to the invention are presented in table 1. The disadvantage of the closest analogue is the low sorption capacity for arsenic compounds.

DESCRIPTION OF THE INVENTION

The objective of the invention and the technical result achieved by using the invention is the development of a new hybrid sorbent with hydrated iron oxides with enhanced sorption kinetics of both forms of arsenic As (III) and As (V).

The stated task and the required technical result are achieved in that a hybrid sorbent based on an anion-exchange polymer matrix with hydrated iron oxides for selective sorption of arsenic, in which hydrated iron oxides are present in the matrix in the form of particles, which are mostly amorphous ferrihydrite, the proportion of which is not less than 80%, and preferably more than 90% of the total mass of hydrated iron oxides, while particles of hydrated iron oxides have a microporous structure, their p zmer varies from 5 to 500 nm, the polymer matrix may be a macroporous fibrous and / or granular material, the content of anion exchange groups in the polymer matrix is not less than 6.0 mmol / g.

A brief description of the drawings.

FIG. 1. Electron micrograph of the starting anion-exchange polymer fiber (1a). Electron micrograph of a hybrid sorbent based on anion exchange PAN fiber with hydrated iron oxides (16).

FIG. 2. The Mössbauer spectrum of a sample of a hybrid sorbent based on PAN fiber with hydrated iron oxides described in example 1.

FIG. 3. The Mössbauer spectrum of the sample hybrid sorbent according to patent US 7,291,578.

FIG. 4. Schedule of kinetics of sorption of arsenic As (III) by a hybrid sorbent with hydrated iron oxides based on PAN fiber described in Example 1, a graph of the kinetics of sorption of arsenic As (III) by a hybrid sorbent with hydrated iron oxides based on a mixture of PAN fiber and ion exchange the resin described in example 3, and the kinetics of sorption of arsenic As (III) hybrid sorbent according to patent US 7,291,578 (trade name F036), selected by the applicant as the closest analogue.

FIG. 5. Schedule of kinetics of sorption of arsenic As (V) by a hybrid sorbent with hydrated iron oxides based on PAN fiber, described in Example 1, a graph of the kinetics of sorption of arsenic As (V) by a hybrid sorbent with hydrated iron oxides based on a mixture of PAN fiber and ion exchange the resin described in example 3, and the kinetics of sorption of arsenic As (V) hybrid sorbent F036 according to patent US 7,291,578, selected by the applicant as the closest analogue.

The inventive hybrid sorbent is an anion-exchange polymer matrix with particles of hydrated iron oxides fixed in it. Moreover, hydrated iron oxides in the hybrid sorbent consist of at least 90% of amorphous ferrihydrite and less than 10% of iron-containing impurities that form a complex of compounds of hydrated iron oxides. Hydrated iron oxides are microporous particles ranging in size from 5 to 500 nm, formed and fixed directly inside the macropores of the anion-exchange material during the destruction of labile iron (III) complexes by treatment with an alkali metal.

As the anion-exchange material, fibrous or granular material, or a mixture of fibrous and granular material in any ratio, can be used. Therefore, the anion-exchange polymer matrix can be a granular anion-exchange resin with secondary or tertiary amino groups, or anion-exchange polymer fibers with secondary or tertiary amino groups, and / or a mixture of resin and fibers, while the content of anion-exchange groups in the polymer matrix is at least 6.0 mmol / g.

As the complex salt, a complex iron salt can be selected where the ligands are oxalate, salicylate, citrate or tartrate. Sodium or potassium hydroxide may be used as the alkali metal hydroxide.

The method of obtaining a hybrid sorbent with hydrated iron oxides is as follows. A solution of the complex salt is prepared, where the ferric cation is the complexing agent, and the carboxylic acid anions are ligands. The resulting solution is added to the anion-exchange polymer matrix for sorption of complex anions on the matrix. After that, the obtained intermediate structure is treated with a solution of alkali metal hydroxide to obtain a hybrid sorbent, which is washed with water.

In the interaction of the anion-exchange groups of the polymer matrix with the anion of the complex salt, an intermediate structure is formed. When the intermediate structure is treated with alkali metal hydroxide, a labile complex — amorphous ferrihydrite — is formed in the phase of the anion-exchange polymer matrix and its decomposition. Since the process of formation and decomposition of the complex proceeds in one solution, the decomposition process proceeds gradually, which allows hydrated iron oxides to begin to form in different distant sections of the polymer matrix, which leads to the formation of smaller particles of hydrated iron oxides. Under these conditions, the formed structure of hydrated iron oxides is more slowly condensed with the removal of alkali metal hydroxide from it, providing the appearance of a large number of micropores in the particles of hydrated iron oxides. The sorption properties of particles of hydrated iron oxides, along with their composition, are determined by the size and porosity of these particles. The smaller the particle size and the higher their porosity, the larger the area of contact of the sorbed substance with the surface of hydrated iron oxides, and thus the sorption capacity. The larger the sorption capacity, the smaller the amount of sorbent required to clean a given volume of water, which expands the possibilities of practical use of the sorbent.

The hybrid sorbent according to this invention has high sorption properties with respect to arsenic compounds of both forms As (III) and As (V), including oxoanions in a wide pH range, arsenate ions and undissociated arsenites. Moreover, the hybrid sorbent is additionally able to efficiently sorb toxic chromium anions Cr (VI), as well as copper and lead cations and hydroxocations. The hybrid sorbent has high sorption kinetics, which makes it possible to increase the linear flow rate of water in the sorption column, which is important for practical use, since it allows for a user-friendly water filtration rate without loss in efficiency.

Examples of hybrid sorbents in the framework of the claimed invention:

Example 1

The base is a macroporous fibrous material - anion exchange resin based on PAN fiber with an anion exchange group content of 8.6 mmol / g.

The proportion of ferrihydrite in the obtained hybrid sorbent is 98%.

The particle size of hydrated iron oxides, including ferrihydrite, is from 80 to 140 nm.

The content of iron (III) in the hybrid sorbent is 63 mg of iron per 1 g of sorbent.

The sorption capacity for As (V) is 32 mg / g (at pH 7).

Sorption capacity for As (III) is 30 mg / g (at pH 7).

Kinetics of As (V) removal - half-sorption time less than 1 min.

Kinetics of As (III) removal - half-sorption time 1 min.

Sorption capacity for Cr (VI) - 250 mg / g (at pH 7).

Cu sorption capacity is 240 mg / g.

Pb sorption capacity is 360 mg / g.

In FIG. 1 is an electron micrograph of the starting anion-exchange polymer fiber (1a) used to produce the hybrid sorbent in Example 1. In the second electron micrograph (1b), a hybrid sorbent based on an anion-exchange polymer fiber with hydrated iron oxides is obtained according to the method described in the invention. Electron micrographs (1b) clearly show particles of hydrated iron oxides on the surface of the fiber.

Example 2

Basis - macroporous granular material - anion exchange resin.

The proportion of ferrihydrite in the obtained hybrid sorbent was 92%.

The particle size of hydrated iron oxides, including ferrihydrite, is from 50 to 120 nm.

The content of anion exchange groups in the hybrid sorbent is 9 mmol / g.

The content of iron (III) in the hybrid sorbent is 72 mg / g.

Sorption capacity for As (V) is 44 mg / g (at pH 7).

The sorption capacity for As (III) is 34 mg / g (at pH 7).

Kinetics of As (V) removal - hemisorption time 25 min.

Kinetics of As (III) removal - half-sorption time 30 min.

Sorption capacity for Cr (VI) - 300 mg / g (at pH 7).

Cu sorption capacity is 270 mg / g.

Pb sorption capacity is 180 mg / g.

Example 3

The basis is a mixture of macroporous fibrous and granular materials in a ratio of 1: 8, respectively.

The proportion of ferrihydrite in the hybrid sorbent was 93%.

The particle size of hydrated iron oxides, including ferrihydrite, is from 50 to 140 nm.

The content of anion exchange groups in the hybrid sorbent is 8.95 mmol / g.

The content of iron (III) in the hybrid sorbent is 71 mg / g.

Sorption capacity for As (V) is 42 mg / g (at pH 7).

Sorption capacity for As (III) - 36 mg / g (at pH 7).

Kinetics of As (V) removal - half-sorption time 1.5 min.

Kinetics of As (III) removal - hemisorption time 4 min.

Sorption capacity for Cr (VI) - 295 mg / g (at pH 7).

Cu sorption capacity is 265 mg / g.

Pb sorption capacity is 200 mg / g.

The type of hydrated iron oxides in the phase of the hybrid sorbents described in examples 1-3 was determined by Mössbauer spectroscopy. In FIG. 2 shows the Mössbauer spectrum of a hybrid sorbent based on an anion-exchange PAN fiber with hydrated iron oxides according to Example 1. It can be seen from the obtained spectrum that the hydrated iron oxides in the sample of the hybrid sorbent according to Example 1 obtained by the method of the invention more than 90% consist from amorphous ferrihydrite Fe ₂ O ₃ ⋅ 3FeO (OH) ⋅ ₃ H ₂ O.

Also, by the method of Mössbauer spectroscopy (Fig. 3), the type of hydrated iron oxides was determined in the hybrid sorbent sample according to the patent US 7,291,578 selected by the applicant as the closest analogue. It can be seen from the spectrum that hydrated iron oxides are composed of magnetic crystalline particles of hydrated iron oxides, including 23% wustite FeO, 28% ferrihydrite Fe ₂ O ₃ ⋅ 3FeO (OH) ⋅ ₃ H ₂ O, 13% hematite α-Fe ₂ O ₃ and 36% lepidocrocite γ-FeO (OH).

From the above data it follows that the hydrated iron oxides in the sample hybrid sorbent obtained by the proposed method, more than 90% consists of amorphous ferrihydrite. At the same time, the hybrid sorbent of the closest analogue according to the patent US 7,291,578 consists of ferrihydrite only by 28%. This once again confirms the great sorption ability of the invention in comparison with the closest analogue.

In FIG. 4 is a graph of the kinetics of sorption of arsenic As (III) by a hybrid sorbent with hydrated iron oxides based on PAN fiber, described in Example 1, a graph of the kinetics of sorption of arsenic As (III) by a hybrid sorbent with hydrated iron oxides based on a mixture of PAN fiber and ion exchange the resin described in example 3, as well as the kinetics of sorption of arsenic As (III) hybrid sorbent F036 according to patent US 7,291,578, selected by the applicant as the closest analogue.

In FIG. 5 is a graph of the kinetics of sorption of arsenic As (V) by a hybrid sorbent with hydrated iron oxides based on PAN fiber, described in Example 1, a graph of the kinetics of sorption of arsenic As (V) by a hybrid sorbent with hydrated iron oxides based on a mixture of PAN fiber and ion exchange the resin described in example 3, as well as the kinetics of sorption of arsenic As (V) hybrid sorbent FO36 according to patent US 7,291,578, selected by the applicant as the closest analogue.

From the graphs shown in FIG. 4 and 5 shows that the highest sorption kinetics, both to compounds of arsenic As (III) and to compounds of arsenic As (V), has a hybrid sorbent with hydrated iron oxides based on PAN fiber described in Example 1 of the invention, namely : The kinetics of 50% sorption of As (III) is 1 minute, and the kinetics of 50% sorption of As (V) is less than 1 minute. Hybrid sorbent with hydrated iron oxides based on a mixture of PAN fiber and ion exchange resin described in Example 3 of the invention has a lower sorption kinetics for arsenic As (III) and As (V). Here, the kinetics of 50% sorption of As (III) is 4 minutes, and the kinetics of 50% sorption of As (V) for it is less than 1.5 minutes. Moreover, the hybrid sorbent according to the patent US 7,291,578, selected by the applicant as the closest analogue, has a sorption kinetics less than example 3, namely, 50% sorption kinetics with respect to As (III) ions - 30 minutes and As (V) - 25 minutes

Table 1 presents the comparative characteristics of the hybrid sorbent closest analogue (US patent 7,291,578) and the claimed hybrid sorbent with hydrated iron oxides.

The sorption capacity of As (III) was determined by (meta) arsenic-sodium sodium NaAsO ₂ , and the sorption capacity of As (V) was determined by (ortho) arsenic-sodium sodium 12-aqueous Na ₃ AsO ₄ ⋅ 12H ₂ O.

As can be seen from the data shown in table 1, the sorption capacity of the inventive hybrid sorbent significantly exceeds the sorption capacity of the hybrid sorbent of the closest analogue (US patent 7,291,578), as well as the sorbents described in the prior art. This is because in the hybrid sorbent with hydrated iron oxides described in the invention, the proportion of amorphous ferrihydrite in the composition of hydrated iron oxides exceeds 90%. Since the functional groups of ferrihydrite, due to its amorphous structure, are more accessible for anions containing arsenic As (III) and As (V) than the structures of crystalline magnetic hydrated iron oxides in hybrid sorbents of the prior art and thus have the highest sorption activity to As ions (III) and As (V), as well as to ions of various heavy metals, such as Cr (VI), Cu and Pb.

As can be seen from the above, of the entire complex of compounds included in hydrated iron oxides, only amorphous ferrihydrite Fe ₂ O ₃ ⋅ 3FeO (OH) ⋅ ₃ H ₂ O has the highest activity for sorption of ions of both forms of arsenic As (III) and As (V) and a hybrid sorbent is additionally able to sorb ions of various heavy metals. The above comparative data prove that the inventive hybrid sorbent with hydrated iron oxides, in which hydrated iron oxides are more than 90% amorphous ferrihydrite, is a highly active and stable sorbent with respect to ions of both forms of arsenic As (III) and As (V) .

In the present description of the invention presents a preferred embodiment of the invention. It can be made changes within the scope of the claimed formula, which makes it possible to widely use it.

Claims (1)

A hybrid sorbent based on an anion-exchange polymer matrix with hydrated iron oxides for selective sorption of arsenic, characterized in that hydrated iron oxides are present in the matrix in the form of particles, which are mostly amorphous ferrihydrite, the proportion of which is at least 80%, and preferably more than 90 % of the total mass of hydrated iron oxides, particles of hydrated iron oxides have a microporous structure, the polymer matrix is a macroporous fibrous and / or granule lined material, the content of anion-exchange groups in the polymer matrix is at least 6.0 mmol / g.

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